The following statements must be true when using System Dynamics techniques to model a system.
When materials, wealth or intangibles accumulate, the cause of the increase is endogenous to the system. Meaning that growth or decay, accumulation or reduction, originates from within the system. When using System Dynamics to build a computer model of a system, the model does not use growth as an external forcing function. The feedback loops within a system cause the stocks to increase or decrease.
When quantities are entered into the flow equations, the results of the accumulations changing over time first needs to be matched against a Reference Behavior Pattern in order to complete the verification and validation of the model of a system.
The growth of anything creates a surplus. The consequences of a surplus might be harmful to humans or beneficial.
The Earth’s natural systems are complex adaptive systems that make forecasting and prediction extremely difficult. For example, increasing human population causes growth in the extraction of material resources from the ground. Also, the increase in consumption per person over time requires an increase in resources and energy.
Do not use any technique that includes IF-THEN or IF-THEN-ELSE logic. This is a way to insert assumptions and external forcing functions into the model without being explicit and transparent about them.
The following statements must be true when using System Dynamics techniques to model a system.